Validate HTML on local machine

I'm currently trying to learn HTML and Java EE Servlet programming. I have an application server running on my local machine (Orion Application Server) and I'm connecting to web pages I've deployed on this server using a browser running on the same machine, directed to http://localhost/mypage.htm (for example).

I know W3C has a site you can go to that will validate an HTML page (and count how many errors are found for a given doctype), but that has to be a publicly available URL. How do you validate HTML on a locally running setup like I've described above?